mozilla-rootcerts-openssl removes ${PREFIX}/etc/openssl/certs on uninstall

[Greg Troxel <gdt%lexort.com@localhost>]

In a thread ok pkgsrc-changes resulting from my editing DESCR, jperkin@
pointed out that

  pkg_delete mozilla-rootcerts-openssl

led to removal of the etc/openssl/certs directory.  This surprised me,
as that directory belongs to the openssl package, not the
mozilla-rootcerts-openssl package.  Sure enough, when I pkg_delete the
certs directory is removed.

I can't figure out why; there is no deinstallation script in the
package, and the certs dir is not in the PLIST.

So is there something wrong with the package, a bug in pkg_delete, or
something else?  Any clues appreciated.